1. Field of the Invention
The present invention relates to a method for producing chemically and color stable cupric hydroxide, suitable for use as a fungicide and as a chemical intermediate. In particular, the method employs a class of carbonate compounds as intermediates and may be characterized as carbonate process cupric hydroxide.
2. Related Art
Cupric hydroxide, depending to a large extent on its method of production may not be a stable material. For example, when a base, such as sodium hydroxide, is added to a solution of water soluble copper salts, e.g., copper sulfate, a blue, gelatinous precipitate is found that gradually turns black in color. This material is unstable and contains cupric oxide hydrate and cupric oxide in addition to cupric hydroxide.
U.S. Pat. No. Re. 24,324 disclosed a method for the preparation of stable cupric hydroxide. This procedure comprised reacting substantially equal molar amounts of copper sulfate and trisodium phosphate, to obtain a copper containing precipitate. The precipitate is then treated with sodium hydroxide in an amount sufficient to convert a major portion of the precipitate to cupric hydroxide. The sodium hydroxide regenerates the trisodium phosphate. The process is continued by alternately adding copper sulfate and sodium hydroxide. The trisodium phosphate is an intermediate and the alternating additions may be repeated 15 to 20 times in this manner.
A solid product is obtained by separating solids, washing and drying them.
Other methods of preparing phosphate-process cupric hydroxide are disclosed in U.S. Pat. Nos. 2,924,505 and 3,628,920.
A particularly effective fungicidal and bactericidal copper material is disclosed in U.S. Pat. No. 3,428,731 wherein stable dispersion of phosphate-process cupric hydroxide are obtained in an aqueous medium by having a pH in the range of about 7 to about 9.5.
This phosphate stabilized cupric hydroxide is suitable for use as a fungicide because of its fine particle size and high surface area, but is not suitable for most industrial applications because of the phosphate ion which has been incorporated in the final product and the resulting insolubles that are found in the reaction medium.
Another approach to producing stable cupric hydroxide is the ammonia-process cupric hydroxide, disclosed in U.S. Pat. Nos. 1,800,828; 1,867,357; 2,525,242; and 3,635,668. These materials are suitable for use as chemical intermediates, however, the individual particles are relatively course and exhibit varying degrees of fungicidal activity. The ammoniacal process also tends to produce cupric hydroxide of higher bulk density and lower surface area than the present method, hence lower reactivity per unit time compared to the present carbonate process cupric hydroxide.
However, inherent in an ammoniacal process is the problem of further processing the effluent, a problem which also exists in the phosphate processes, since both of the waste water materials may not be appropriate materials for discharge. For example, in the so called "bug ponds" where waste water is treated, ammonia may be a biological poison, which damages the effectiveness of the bacteria in the pond, whereas the phosphate may enhance undesirable algae growth. The ammoniacal process is further complicated in waste water treatment in that ammonia solubilizes the cupric hydroxide to a significant extent, thus further contaminating the waste water with copper and reducing the copper content of the product.
Phosphate-process cupric hydroxide does not present a problem in regard to copper solubility, but the phosphate may interfere with the surface properties (phosphates are surfactants) with respect to coagulation and flocculation in waste water treatment.
A disadvantage of the cupric carbonate as an industrial (chemical) intermediate (where a basis is required) is excessive foaming of the reaction medium, necessitating careful control of the copper compound addition. The carbonate process cupric hydroxide of the present invention give rise to little or no foaming and in fact, the slight effervescing of the present cupric hydroxide particles due to occluded carbonate serves to increase the reaction rates due to the so called "exploding" effect in the particles which serves to further divide and disperse the particles.
The present method has a significant advantage over the related art in that neither ammonia, copper nor phosphate are introduced into waste water. Another advantage is the presence of carbonate in the waste water, which is a practiced and accepted method of buffering industrial effluents. A feature of the present invention is absence of pollutants in the waste water stream. Another advantage of the present method is the production of the fine particles of low bulk density and high surface area. A further advantage is the use of aqueous dispersions of the carbonate process cupric hydroxide directly as foliage sprays without stickers (adhesive aids, such as starch). A further advantage of the product of the present method is its use as an intermediate in the production of various industrial copper chemicals such as copper acetates, formates, naphthenates and the like.
A particular feature of the use of the carbonate process cupric hydroxide as a chemical intermediate is the excellent reaction rates from high surface area and low foaming.